This invention relates to a process for preparing a polymer emulsion containing colloidally suspended therein an interpenetrating polymer network wherein a first polymer network is intertwined on a molecular scale with a second polymer network and optionally additional polymer networks. The polymer emulsion of this invention is useful as binder of fibers or fabrics, especially fiberfill.
Fiberfill is a generic term used to describe a variety of nonwoven fabrics for a variety of end uses. The common feature of all fiberfill products is a measure of loft or thickness in the fabric. This loft is a characteristic of value because it imparts insulation to outerwear and bed quilt stuffing, cushioning in furniture padding, dust holding capacity to filter media and resiliency to scrubbing pads. The most common construction of a fiberfill product is a loosely garnetted, cross-lapped or air laid web of 6 to 30 denier polyester staple fibers which is bonded (locked in its particular fiber arrangement) by an emulsion polymer binder. Fiberfill products can be made with other fibers, e.g. polyamide, cellulose acetate, rayon, glass, alone or in blends with each other. Some fiberfill is sold without a bonding agent but the material will lack durability, tensile strength and resiliency when compared to a bonded product. Bonding methods other than emulsion polymers, such as needle punching, and meltable fibers and powders are also used, but the polymer emulsion method produces the optimum strength/loft ratios for the majority of fiberfill markets.
The polymer emulsion product used as the binder is usually one of the following chemical types: polyvinylacetate, acrylic copolymers, styrene-butadiene copolymers or polyvinylchloride. Polyvinylacetate is the most common binder and in recent years it has been made white enough and strong enough to replace most of the acrylic polymer traditionally used. Polyvinylchloride is used where flame resistance is of prime concern and styrene-butadiene copolymers are used for special rubbery applications.
The characteristic of initial loft is unaffected by the chemical type of the binder used. However, initial loft is not the loft of value. Fiberfill products in their normal use are compressed, reducing the initial loft, and released many times. The true value of loft is how thick the fiberfill web is after repeated compression/recovery cycles. One drawback of current polymer bonded fiberfill technology is that temperatures over 100.degree. F. will soften the binder and cause the fiberfill product to permanently lose loft if it is compressed at this elevated termperature. Temperatures of up to 180.degree. F. are encountered in the shipping and use of many fiberfill products. Typically a fiberfill product, which may lose only 15% of its initial loft if compressed and released at 80.degree. F., will lose more than 80% of its loft if tested the same way at only 120.degree. F. Higher termperatures are expected to even more dramatically damage this loft recovery.
The polymer emulsion prepared by the process of this invention provides a binder compound for fiberfill which provides improved resiliency and loft recovery to the bonded fiberfill products. This polymer emulsion is useful in bonding textile fibers in a fiberfill product or in any nonwoven product or even any traditional woven or knitted textile fabric.